The Lake Massaciuccoli is one of the largest and most important wetlands of Italian peninsula and is included in a protected area of regional and international relevance. In the present study, an update of the knowledge on aquatic and hygrophilous vegetation has been carried out, according to the phytosociological method. Some ecological analyses of the water trophism have been carried out, showing the high trophic level of the lake waters. The vegetation survey allowed to identify 31 plant communities belonging to 10 vegetation classes: Lemnetea minoris, Potametea pectinati, Bidentetea tripartitae, Isoëto-Nanojuncetea, Littorelletea uniflorae, Phragmito australis-Magnocaricetea elatae, Scheuchzerio palustris-Caricetea nigrae, Galio aparines-Urticetea dioicae, Molinio-Arrhenatheretea and Alnetea glutinosae. Aspects with Sphagnum sp. and other Bryophytes, present in small patches within the peculiar floating reed beds of the Thelypterido-Phragmitetum association, have been recorded and analyzed. A new association (Samolo valerandi-Eleocharitetum caducae) has been described. Nine Habitats of conservation interest have been identified; among them, two (Natura 2000 codes: 7210 and 91E0) are considered of priority interest.